The invention relates to a horizontal metal extrusion press, between whose cylinder crosshead and platen or counter-crosshead, which are connected by tie rods, a billet receiver holder and a moving crosshead are guided in a horizontally movable manner. The counter-crosshead which supports the extrusion die during direct extrusion via a die holder and during indirect extrusion via a hollow ram--the die ram, the moving crosshead which is connected to the plunger piston and carries and guides the press ram or a closure piece during indirect extrusion, and the receiver holder have to be aligned with the press axis and guided in such a manner that they retain their alignment in the course of production, particularly throughout the extrusion process, for which purpose adjusting and measuring devices are provided. These adjusting and measuring devices should be capable of checking the in-line axial alignment of receiver and extrusion tools (die, ram and--in the case of hollow extrusion -mandrel) during each extrusion cycle and resetting it in the event of variations owing to changed operating conditions. Commensurate with the critical importance of alignment of receiver and extrusion tools for trouble-free operation of the press and for product quality in general and for multiple and hollow extrusion in particular, there has been no lack of proposed methods of achieving this.
Thus, it is known from German patent document, which corresponds to U.S. Pat. No. 3,808,859, DE-OS 22 38 509 to provide the receiver or the receiver holder, at its end facing the moving crosshead with the press ram, with measuring instruments which detect the radial position of the press ram relative to the receiver in planes which are perpendicular to one another, so that it is possible to center the press ram relative to the receiver at the one end face of the receiver, while centering of the extrusion die in relation to the other end face of the receiver is effected by a central recess in the receiver serving as a seat for the die holder. Centering of the press ram relative to one end face and of the extrusion die relative to the other end face of the receiver, however, does not mean that the axes of press ram, receiver and extrusion die are in alignment, with the result that additional measurements are necessary, such as that of the inclination of the receiver relative to the counter-crosshead, possibly combined with monitoring of the alignment of the press ram relative to the bed plate of the press, along with the constructional outlay and sources of error that this entails.
From German patent documents DE-OS 28 50 576 and DE-OS 30 20 156 a measuring device is known, in which a carrier connected to the press ram carries two transmitters emitting coherent beams of electromagnetic radiation which are parallel to one another and to the press axis, while there are associated with the receiver holder and the die holder, on carriers connected to these holders, radiation receivers which are at the same distance from one another and from the press axis as the transmitters. This solution did not prove successful under operating conditions because it was shown to be susceptible to faults and obstructive and so did not justify its high constructional outlay.
An apparatus which is better adapted to the operating conditions is that according to European patent document EP-A2-0 379 937 in which the receiver holder and the moving crosshead, between the tie rods connecting the cylinder crosshead and the counter-crosshead to form the press frame, are provided with bottom guides taking up the weight and with top hold-down guides, associated with which guides are detecting elements which measure and indicate the position of the receiver holder and the moving crosshead relative to the tie rods. In order to calibrate the detecting elements, the receiver and receiver holder and extrusion tools have to be aligned in advance, which alignment has to be repeated for each tool combination, this being a drawback particularly when press programs of small batch sizes are being run.